Obesity prevention is a top priority of researchers, clinicians, and policy makers. Even young children have not been spared this epidemic, and obesity in young children leads not only to short-term morbidity but also to later obesity and its adverse consequences. Thus it is critical to identify modifiable determinants of obesity that exist very early in life, even before birth. In this proposed competing continuation of R01 HD34568, our overall goal is to examine the roles of prenatal dietary and hormonal factors, infant feeding, and postnatal growth in the genesis of adiposity-related outcomes at the age of 7 ears. The main study outcomes will be total and regional fat mass assessed by dual x-ray absorptiometry (DXA), and plasma adiponectin levels. This study will extend and amplify a body of work from the first five years of funding for Project Viva, a prospective longitudinal study of pregnant women and their children. While some studies have examined associations of birth weight with later obesity, birth weight is but a momentary marker, an integral of numerous determinants operating before birth. In this proposal, we will "go beyond birth weight" to focus on two endocrine factors operating prenatally. glucocorticoids and leptin. as well as maternal intake of long- chain polvunsaturated fatty acids, that could be involved in the development of obesity in the offspring. The role of breastfeeding in obesity prevention has taken on new urgency in the 21st century. In this study, we will address the validity of epidemiologic associations between breastfeeding and later adiposity-related outcomes, both by carefully controlling for potential confounding by sociocultural factors and by evaluating plausible mechanisms, including behavioral and metabolic effects. We will also address the extent to which any associations of accelerated infant growth with later adiposity can be ascribed to metabolic pathways operating prenatally or to infant feeding practice. By following to age 7 years participants originally recruited prenatally and followed prospectively as part of Project Viva, the proposed project is uniquely poised to examine events occurring in the pre- and peri-natal period as critical to the development of obesity in childhood. The results of this study promise to unravel some knotty epidemiologic issues in the early origins of obesity, and to open up new potential avenues for primordial obesity prevention.